Field of the Invention
This invention relates to rack and pinion type steering gear devices, and more particularly to a rack and pinion type steering gear device having a rack guide for applying a preload to the meshing engagement of tooth surfaces of a rack and a pinion.
In many cases, the conventional rack guides are made of metallic materials through sintering and forging processes. However, these metallic rack guides are disadvantageous in that metallic striking sounds such as knockings occur during running of a vehicle on a rough road and the like.
Description will now be given of the causes with reference to FIG. 1.
Referring to FIG. 1, a pinion 1 is mounted on the forward end of a steering shaft, not shown, and a rack 2 is in mesh with this pinion 1.
A rack guide 3 is formed of a metal material and urges the rack 2 from behind the rack 2 for applying a preload to the meshing engagement between the pinion 1 and the rack 2.
Threadably coupled to a rack housing 5 is a nut 4, which is adapted to hold the rack guide 3 at a proper position through a spring 6.
Normally, a clearance .DELTA.t is formed between the rack guide 3 and the nut 4 so that the rack guide 3 can avoid interfering with the nut 4 as the rack 2 slides. In this steering gear device having the above-described arrangement, when an external force F.sub.1 in the axial direction of the rack 2 from a road surface is applied, there occurs a force F.sub.2 in the axial direction of the rack guide as being a component of a pressure angle of the rack due to a reaction force of the pinion, whereby the rack guide 3 impinge on the nut 4, and subsequently, the rack 2 is returned through the resiliency of the spring 6 so that the pinion 1 impinges on the rack 2. This phenomenon is imparted to the driver as the knocking sounds. In passing, only the rack housing 5 is shown in cross section in FIG. 1.